Rotor blade locking



June 9, 1953 P. D. COMERY ETAL ROTOR BLADE LOCKING Filed March 17, 1951mvzlvrons RD conmy .zrPanv/s fiTTOR/VEY Patented June 9, 1953 U NITEDSTATES "FATENT O'FlF l-Ci-E ROTOR BLADE LOCKING Tet-er lDennis Comery,Cooksville, Ontario, and

Joseph .'1hompson Purvis, North York Township, York Coun'ty, Ontario,Canada, assignor's to A. V. Roe Lana'da Limited, Malton, Ontario,=Ganada,.a corporation ApplicationMarchli, 1951, .SerialNo. 216,146

3 'Cla'ims. (Cl. 253'--77) l This invention relates to Mailing forrotary power conversion'machines andtheflike and more particularly to animproved fastening device for such 'blading.

Blading of this type normally requires such accuracy of form and finishthat the blades have to be manufactured individually. This practice,

however, "introduces fresh problems in connection with the mounting ofthe blades in the machine, problems which are particularly critical 1 ifthebladeis to be mounted on-a compressor or turbine rotor which will berotating at high speed. Not only is centrifugal loading imposed upon theblade under these conditions but there is also axial loading 'due to themomentum of the working fiuidand although this axial loading is usuallysmall'in "comparison-with the centrifugal loading some provision mustnevertheless be made to absorb it.

Although there have been various locking 'devices developed 'for thispurpose, for the most part these fail to provide positive location 'of;the blade relative to :its mounting. In addition, their use usual-1yentails more or less complicated machining of the rotor or 01 the bladeroot itself, and particularly is this true when some form of lockingwire is used.

It is the object of this invention to provide improved retaining meansfor withstanding this axial loading.

The invention will be more readily understood by reference to theaccompanying drawings which form a part of this specification and 'inwhich like reference characters denote like parts throughout the same.In these drawings,

Figure 1 illustrates a gas turbine engine having a turbine rotor withblades such as those with which the invention is concerned attached"thereto,

Figure '2 is 'a fragmentary View of a rotor blade held in the rotoragainst axial movement by a "locking device in accordance with theinvention,

between them. The turbine assembly comprises a rotor 13 supporting aseries of radially-extending blades M, the blades being mounted in aseries of peripheral slots I 5, which in the embodiment illustrated areof fir tree cross-section as best seen in Fig. 3'; the slots extend from"the front face it of the rotor to its rear face H in a substantiallyaxial direction. I

The blades themselves are formed with blade roots l8 of fir tree shapewhich conform to the shape of the slots 1'5, each root terminating atthe base in the basal extremity or tip Ii). An integrally formed lug orstop 26 projects perpendicularly from the tip 1-9 of the root at theforward face 2i of the root and the root is slotted transversely toprovide a recess 22. The root tip is is machined fiat to provide anindented por- -=tioi.i se between the recess 22 and the rear face 2-3 ofthe root to leave 'a space M between the root Hi and the base of theslot Iii in the assembled position.

Figures 4 and 5 illustrate a preferred form of a locking strip 2:; whichmay be formed from a flat metal blank; the strip has rectangular andtabs 23 and 2''! of substantially equal width and an intermediateportion or plate 23 whose width is materially greater than that of theend "portions. plate '28 is centrally dished to provide a "dimple 2 9whose depth is very slightly greater than the depth of the space Mprovided between the root is and the base of the slot it. One tab 26 of"the strip 25 is bent through a right angle to provide a projectionextending outward- 1y on the side which is opposite to the projectiono'f-the dimple 29 the tab 23 is slightly shorter in length than thedepth of the recess 2'2. The proportions of the strip 25 aresuch'thatwhen it is disposed in the space 24 with the tab 2% projecting intotherecess 22, the remote extremity of the-plate 328' will belocated justshort of'the rear face I? of the rotor.

In attaching a blade'to the turbine rotor it, the locking strip 25 isfirst fitted into the space 24 .on the bottom :of the blade root it withthe projecting tab 28 of the strip extending into the recess '22. bladeroot is then slid rearwardly into one 0f the mating slots 1:5 in therotor until the projecting lug 2 on the blade encounters the front face:of the rotor, and the blade being thus positioned, :the :tab 21'! onthe strip '25 is bent through-a :right'angle'to engage the rear face ll.of the rotor. .By making the intermediate. portion or plate 2:8 widerthan the extended tab 2? the bend in the strip tends :to occur along theline between .the plate and the tab, and by judic'ious cho'ice of "the"length of the central portion the line-of the bend is so positionedthat the rear face I 7 of the rotor will-be tangential to theinnerradius of the bend. Further, it is possible to 55 achieve a larger'ben'd"radius at this point by having the depth of the space 2 greater thanthe normal thickness of the undimpled portion of the strip and disposingthe dimple on the rotor side of the strip, that is, on the same side asthe center of curvature of the final bend so that the centre ofcurvature will be located ahead of the rear face of the rotor.

The projecting lug 26 therefore provides positive restraint againstrearward movement of the blade in the slot While the bent tab 27! holdsthe blade against movement along the slot in the opposite sense. acompressive force against the respective faces of the blade root and therotor on opposite sides of the space 24 and this force assists inmaintaining the relative positions of the blade and therotor.

The projecting element 26 may be replaced by similar elements on thefront or rear faces of, either the blade root or the rotor, the recess22 and the space 24 being positioned correspondingly, and it is to beunderstood that the form of the invention herewith shown and describedis to be taken as a preferred example of the same and that variouschanges may be made in the shape, size and arrangement of the partswithout departing from the spirit of the invention or the scope of thesubjoined claims.

What we claim as our invention is:

1. A locking device for a blade of a rotary power conversion machinehaving a blade supporting member and blades provided with blade rootmembers whereby they are demountably secured to the supporting member,the said members each having exposed opposite end faces and being inslidable relationship in a direction extending between the end faces andin interlocking relationship in another direction, comprising a stopelement projecting from one and engaging the other of the said membersto provide positive relative location of the root member with respect tothe supporting member and with respect to one sense of the direction ofslidable relationship, one of the said members having a recess locatedintermediately of its opposite end faces, and means cooperating with therecess for preventing relative movement of the root member with respectto the supporting member in the other sense of the direction of slidablerelationship, which means includes a plate dis-,

posed between the said members and having projecting tabs at oppositeedges, the plate having a thickened portion at which the opposite facesof the plate bear upon the said members. one of the tabs extending intothe recess in the recessed member and the other of the tabs engaging anexposed face of the member not so recessed, the said other tab beingbendable at the margin of the plate after assembly to so engage the saidface.

2. A locking device for a blade of a rotary power conversion machinehaving a blade supporting member and blades provided with blade rootmembers whereby they are demountably secured to the supporting member,the said members each having exposed opposite end faces and bein inslidable relationship in a direction extending between the end faces andin interlocking relationship in another direction, the said membershaving adjacent basal surfaces extending between the opposite end facesand facing each other, comprising a stop element projecting from one andengaging the other of the said members to provide positive relativelocation of the root member with respect to the supporting In addition,the dimple 29 exerts member and with respect to one sense of thedirection of slidable relationship, one of the said members having arecess extending from the basal surface of the recessed member into thebody of the recessed member at a location spaced from its opposite endfaces, the basal surface of the recessed member being cut away betweenthe recess and one of the exposed end faces to provide a space betweenthe basal surfaces, the depth of the said space being less than thedepth of the recess, and means co-operating with the recess forpreventing relative movement of the root member with respect to thesupporting member in the other sense of the direction of slidablerelationship, which means includes a locking strip disposed in the saidspace between the basal surfaces of the said members, the strip beingformed from a relatively thin metal blank and being of materiallygreater width over a portion intermediate of the ends than the width ofthe end portions to provide an intermediate plate and projecting tabs atopposite ends of the plate, the plate being dished to increase thethickness of the strip beyond its normal thickness, the normal thicknessof the strip being less than the depth of the said space between thebasal surfaces and the dished portion of the strip being compressedbetween and tightly engaging the said basal surfaces, one of the tabsextending into the recess in the recessed member and the other of thetabs engaging an exposed face of the member not so recessed, the saidother tab being bendable at the margin of the plate after assembly to soengage the said face.

3. A locking device for a blade of a rotary power conversion machinehaving a blade supporting member and blades each provided with a bladeroot member whereby they are demountably secured to the supportingmember, the said members each having exposed opposite end faces andbeing in slidable relationship in a direction extending between the endfaces and in interlocking relationship in another direction, the saidmembers having adjacent basal surfaces extending between the oppositeend faces and facing each other, comprisin a stop element projectingfrom one and engaging the other of the said members to provide positiverelative location of the root member with respect to the supportingmember and with respect to one sense of the direction of slidablerelationship, one of the said members having a recess extending from thebasal surface of the recessed member into the body of the recessedmember at a location spaced from its opposite end faces, the basalsurface of the recessed member being cut away between the recess and oneof the exposed end faces to provide a space between the basal surfaces,the depth of the said space being less than the depth of the recess, andmeans cooperating with the recess for preventing relative movement ofthe root member with respect to the supporting member in the other senseof the direction of slidable relationship, which means includes a stripdisposed in the said space between the basal surfaces of the supportingmember and the blade root, the strip being formed from a relatively thinmetal blank and being of materially greater width over a portionintermediate of the ends than the width of the end portions to providean intermediate plate and projecting tabs at opposite ends of the plate,the plate being dished to increase the thickness of the strip beyond itsnormal thickness, the normal thickness of the strip being 5 less thanthe depth of the said space between the basal surfaces and the dishedportion of the strip being compressed between and tightly engaging thesaid basal surfaces, one of the tabs extending into the recess in therecessed memher and the other of the tabs engaging an exposed face ofthe member not so recessed, the said other tab being bendable at themargin of the plate after assembly to so engage the said face, theconvex face of the plate being on the 10 same side of the strip as thecenter of curvature of the bend whereby the bend will be spaced from thebasal surfaces of the last mentioned member and the blade root and theradius of the bend will be greater than if the bend were not so spaced.

PETER DENNIS COMERY. JOSEPH THOMPSON PURVIS.

No references cited.

